Spherical plain bearings typically comprise a ball positioned for rotational movement in an outer race. The outer race defines an inner surface contoured to receive and retain the ball therein. In one type of spherical plain bearing, the outer race is swaged around the spherical outer surface of the ball. These types of spherical plain bearings tend to provide suitable performance in low friction applications. In some cases, particularly those in which the ball and the outer race are each metallic, however, the outer race may be constructed with a slot to permit insertion of the ball. Such bearings are referred to as “load slot bearings.”
The manufacture of load slot bearings generally involves a case hardening process to produce bearing elements having different hardnesses. Lapping or grinding of the outer race may also be employed to produce a bearing having the desired morphological surface characteristics for effective interaction between the outer race and the ball. Also, load slot bearings may include provisions for grease lubrication or use of a dry film lubricant to reduce the friction between the ball and the race. In load slot bearings in which grease lubrication is employed to reduce the friction, the bearing is subject to prescribed maintenance at scheduled intervals. Non-compliance with the prescribed maintenance or with the schedule of maintenance can increase bearing wear and can compromise the life of the bearing. In particular, improper maintenance such as insufficient lubrication can have an impact on bearing operation and promote galling, fretting, and/or other types of wear.
A typical link apparatus fastens or connects one device to another device. Often, one or both ends of the link apparatus must bear a vibratory load under only slight oscillatory motion. Bearing assemblies, typically load slot bearings or spherical plain bearings, are disposed in one or both ends of such a link apparatus. In certain applications, particularly high-temperature applications, the link apparatus and the bearing assemblies disposed therein must meet rigorous material and mechanical properties related to friction, lubrication and wear.